Your boiler has lost its internal identity chip and can no longer recognize its own settings or model type.

Coding plug not detected.

What causes this fault?

This fault occurs when the small 'identity chip' known as the code plug becomes loose or fails electronically, meaning the boiler can no longer remember which model it is or what its safety settings should be. It is most commonly caused by a physical connection failure at the chip's socket or a breakdown of the internal circuitry on the main control board.